Distortion reducing means for jaw portion of compression tool

ABSTRACT

The cross straps of a heavy-duty compression tool are provided with extended nose portions that bear against both sides of both jaw members for a substantial distance forward of the strap pivots. A parallel walled slot is provided between the extended nose portions to receive the work. The function of the extended nose strap is to reduce if not eliminate out of plane distortion of the jaw members thereby not only improving the ability of the tool to perform its function, but at the same time reducing the handle load and the strain imposed on the various portions of the tool.

United States Patent 3,410,129 11/1968 Werner Thomas M. Porter Concord, Mas. 788,583

Jan. 2, 1969 Apr. 13, 1971 11. K. Porter, Inc. Somerville, Mass.

Inventor Appl. No. Filed Patented Assignee References Cited UNITED STATES PATENTS Primary Examiner-Charles W. ,Lanham Assistant Examiner-Michael .1. Keenan AttorneyPorter & Meyer ABSTRACT: The cross straps of a heavy-duty compression tool are provided with extended nose portions that bear against both sides of both jaw members for a substantial distance forward of the strap pivots. A parallel walled slot is provided between the extended nose portions to receive the work. The function of the extended nose strap is to reduce if not eliminate out of plane distortion of the jaw members thereby not only improving the ability of the tool to perform its function, but at the same time reducing the handle load and the strain imposed on the various portions of the tool.

Patented April 13, 1971 3,575,037

3 Sheets-Sheet 2 FIGZ INVENTOR THOMAS M. PORTER BY Q W ATTORNEYS Patehted A ril 13, 1971 3,575,031

3 Sheets-Sheet 3 4 I I I M m I I I M T1 '1]. l8

' FIG. 4

FIG. 5

INVENTOR THOMAS M. PORTER ATTORNEYS IDIIS'IORTION REDUCING MEANS FOR JAWPORTION 'OF COMPRESSION TOOL SUMMARY OF THE INVENTION This invention relates generally to heavy-duty compression tools such as boltor wirecutters and crimping tools.

Generally such tools comprise a jaw portion consisting of two jaw members pivotally joined at intermediate portions to a pair of cross straps to permit a limited rotation of the jaw members relative to the cross straps and to each other. Normally the inner edges of the two jaw members are each provided with intermeshing gear segments in the region edges provided at the forward ends of the jaw members.

Indeed for example, in a strain analysis carried out in connection with the development of a cutting tool of the present invention cutting forces in excess of 18,000 pounds have been measured at one of the cutting edges with a handle load of I55 pounds in a typical heavy-duty cutting tool. I

Even though the design and structure of suchtools has been refined and perfected with years of practical experience, and the jaw members are forged from high quality tool steel and are carefully shaped and hardened, difficulty has been experienced, with cutting tools in cutting certain things such as guy strand wire or bolts having deep threads. These difficulties are of the nature of the inability of the tool to complete a cut in some instances; the chipping of the cutting edges; and even in rare instances the fracture of the jaw member, particularly through the section containing the hole for the cross strap pivot and the gear teeth. In the case of crimping tools, a scissoring effect has been noticed especially with tools having long nose multigroove jaws.

It has been discovered that a major cause of such difficulties is the out of plane distortion of the jaw members at the working portion forward of the straps. In the case of seven strand guy wire for example where the wire is formed of seven relatively small strands of very hard wire twisted together, the closing of the cutting edges during a cutting operation tends first to flatten out the twisted strands in the region between the cutter blades. This frequently results in one or more of the strands passing between the cutting edges at-a substantial angle which tends to displace the cutting edge portions of the jaws relative one to the other. In the case of a bolt with a large thread having a deep groove there is a tendency for each cutting edge to slide down the side of the groove with which it comes into contact. Since the position of the groove on one side is displaced from the position of the groove on the other side this tends to develop an out of plane force and an out of plane displacement.

In either case the magnitude of the problem appears to be increased if the cutter edge portions of the jaw are even slightly misaligned for example in the order of 0.01 inch or so. No matter how closely tolerances are maintained in the manufacturing process it is almost impossible to prevent completely some degree of misalignment of the cutting edges due to the variations inherent in the process of forming the jaw members and sharpening the cutting edges.

Once the cause of the occasional difficulty in cutting was discovered, measurements were made and it was ascertained that in the case of a particular cutting tool where the overall length of a jaw member was about 7% inches, where the distance between the top and the center line of the straps (as measured at the center line of the strap pivot) was about 2% inches, the maximum width of the jaw member was about 2% inches, the width of the strap was about 2 inches and the thickness of the jaw member and of the strap was about onelt'alf inch the outof plane deflection at the tip of the cutting edges in particular instances exceeded one-sixteenth inch. On the other hand a subsequent strain analysis indicated that the maximum out of plane deflection under similar conditions that could be attributed to the out of plane bending of the jaw members themselves would only be in the order of 0.002 inch. Obviously, therefore, the total out of plane deflection is attributable to many factors beside the out of plane bending of the jaw members themselves. In view of this it is apparent that the obvious solution of merely making a more massive cutting tool for the same job would not be particularly effective and would lead to a weight increase which would be quite undesirable.

It is the object of this invention to provide means of reducing, if not eliminating, the out of plane distortion of the cutting edges of a heavy-duty cutting tool without appreciably increasing the weight thereof.

This and other objects of the invention will better be understood from the detailed description which follows and from the drawings in which:

REFERENCE TO THE DRAWING FIG. I is a plane view of a typical contemporary heavy-duty toggle handle cutting tool;

FIG. 2 is a plan view of the-jaw assembly of the cutting tool of the present invention;

FIG. 3 is a side elevation of the jaw assembly of FIG. 2;

FIG. 4 is a front elevation of the jaw assembly of FIG. 2; and

FIG. 5 is a plan view of the extended nose strap of the present invention.

DETAILED DESCRIPTION Referring then to FIG. I which as mentioned above, shows a conventional toggle-handled cutting tool in common use at this time, the handle portion is indicated generally at I] and the jaw portion is indicated generally at 12. Handle portion 11 consists of two handle members 13 and 14 which are only partially shown to save space. In a typical tool the handle may be as long as 3 or 4 feet long depending on the size of the tool. Handle members I3 and 14 are conventionally covered with an insulating sleeve of some insulating material such as a fiber glass reinforced plastic indicated at 15 and 16 respectively.

Jaw portion 12 consists of two jaw members 17 and 18 respectively pivotally joined at strap pivots 21 and 22 respectively to upper strap 23 and lower strap 24 (not shown in FIG. I). Jaw member 17 comprises cutter blade portion 25 which includes the cutter blade 26 and lever portion 27. Jaw member 18 comprises cutter blade portior 28 which includes cutter blade 29 and lever portion 31.

Handle member 13 is joined to jaw member 17 atjaw pivot 32 and handle member 14 is joined to jaw member 18 at jaw pivot 33. In addition handle member 13 is joined to handle member 14 at toggle pivot 34. Pivots 32, 33 and 34 consists of bolts secured by nuts (not shown). In the particular embodiment shown handle member 13 is in the vicinity of jaw pivot 32 divided into an upper and lower planar extension indicated at 35 between which the extremity of the lever portion 27 of jaw member 17 extends. Likewise handle me'mber M is in the vicinity of jaw pivot 33 divided into an upper and a lower planar extension indicated at 36 between which the extremity of the lever portion 31 of jaw member 18 extends. Jaw pivot 32 extends through mating apertures provided in extension 35 of handle member 13 and at 37 in lever portion 27. Jaw pivot 33 extends through mating apertures provided in extensions 36 of handle member 14 and at 38 in lever portions 31.

The toggle link is formed by providing handle member 14 with a pair of inwardly extending planar extensions indicated at 39 between which an inwardly extending tongue 41 provided on handle member 13 extends. Toggle pivot 34 passes through mating apertures provided in extensions 39 and tongue 41. The inner edge of handle member 13 is provided with a stop member 42 adapted to contact a portion of the inner side of handle member 14 to limit the degree of closing between handle members 13 and 14 about toggle pivot 34.

To provide for the adjustment of the tool after assembly and in use so as to insure that cutter blades 26 and 29 will just come into contact with each other as stop member 42 abuts the inner edge of handle member 14, provision is made in the tool as shown to move the position of jaw pivot 33 relative to toggle pivot 34. This is accomplished by providing handle member 14 in the vicinity of jaw pivot 33 and toggle pivot 34 with a slot that divides that portion of the handle member 14 into two arms, one indicated at 43 carrying jaw pivot 33, and the other indicated at 44 carrying toggle pivot 34. Arms 43 and 44 are sprung apart to the desired degree by means of adjusting bolt 45 which passes through a tapped aperture in arm 43 and abuts the side of arm 44. Bolt 45 is provided with a locknut 46.

In the conventional heavy-duty cutting tool as shown in FIG. 1 each of the cross strap members 23 and 24 of jaw portion 12 is essentially rectangular in configuration both in plane view and in cross section, although the ends, as viewed in plane view, may be rounded slightly as shown to obtain the maximum effective width without there being any portion of the strap member which extends beyond the edge of the jaw member. The function of the two straps of course is to tie the two strap pivots together in fixed relation. In so doing, however, the straps are the major load bearing members in the combination with stresses as high as 105,000 p.s.i. having been measured in portions of the straps in the strain analysis mentioned above. Straps 23 and 24 each normally have a thickness of about three-fourths the thickness of the jaw members 17 and 18, and a width between one-eighth and onefourth the length of the jaw members.

Strap pivots 21 and 22 are bolts which pass through mating apertures provided in upper strap 23 and in jaw members 17 and 18 respectively and engage in mating tapped apertures provided in lower strap member 24. A lock plate 47 having multisided apertures adapted to engage the side of the head of each of pivots 21 and 22 in a plurality of different positions is provided to lock strap pivots 21 and 22 in position once they have been tightened to the desired degree. Lock plate 47 is held in position on upper strap 23 by means of lock plate screw 48 which is provided with a lock washer and engages in a tapped aperture provided therefor in strap 23. The forward end of lock plate 47 toward cutting blades 26 and 29 may be provided with a portion extending beyond strap 23 which acts as a guard member and with throat spring 49 both designed to keep the work to be cut from extending beyond the limits of cutter blade portions 26 or 29.

The modifications comprising the present invention are shown in detail in FIGS. 2, 3, 4 and 5. Since these modifications effect only the upper and lower strap and the lock plate all other parts will for simplicity retain the same reference numbers. Also for simplicity the handle portion 11 which is unchanged is omitted in its entirety from the showing.

In the modifications of the present invention upper strap 51 and lower strap 52 which are substantially identical and symmetrical left to right are each provided with a pair of extended nose portions 53 and 54 (and 53' and 54) adapted to overlie substantially all of jaw members 17 and 18 forward of the strap pivots in cutter blade portions 25 and 28 respectively. Between extended nose portions 53 and 54 there is provided a parallel walled slot 55. The centerline of slot 55 is centered on the contact line between cutter blade 26 and cutter blade 29 and the width of slot 55 is but slightly in excess of the diameter of the work that the particular cutting tool is designed to cut. Thus in the case of a tool designed to cut inch wire or 9% inch bolts the width of slot 55 is twenty-one thirty-seconds of an inch. Slot S5 is preferably terminated in a semicircle so located that the entirety of slot 55 is within the area encompassed by cutter blades 26 and 29. This eliminates any need for a guard portion or a throat spring on lock plate 56.

Lock plate 56 is secured to upper strap 51 by means of lock plate screw 48 which engages tapped aperture 57. The

apertures in straps 51 and 52 for strap pivots 21 and 22 are indicated at 58 and 59 respectively. Apertures 58 and 59 in lower strap 52 are tapped to retain the ends of pivot bolts 21 and 22, while apertures 58 and 59 in upper strap 51 are sized to pass these bolts.

The wiping side of each of the straps 51 and 52 intended to lie next to jaw members 17 and 18 is finish ground to ensure a flat surface and to minimize binding. The upper and lower surfaces of jaw members 17 and 18 are similarly finish ground for the same reason. The purpose is to have as close a fit between the wiping surfaces of the strap members and the corresponding portions of the jaw members as possible so that the strap members 51 and 52 can effectively support jaw members 17 and 18 and prevent any distortion of jaw members 17 and 18. This does not mean however that the contact between the surfaces necessarily must be continuous, and if desired interior portions of the wiping face of straps 51 and 52 away from the periphery thereof may be removed, (Le. recessed) if desired to reduce both weight and frictional resistance provided sufficient contact areas remain to effectively reinforce the jaw members.

Similarly to reduce weight the forward end of extended nose portions 53 and 54 may be reduced in thickness relative to the main body of strap members 51 and 52. Preferably this is accomplished as shown, by tapering the forward end of nose portions 53 and 54 slightly beginning at about the end of slot 55. However to insure that the requisite strength and stiffness is preserved one or more reinforcing ribs indicated at 61 and 62 may be retained on each of extended nose portions 53 and 54. Preferably these reinforcing ribs are maintained at the height of the main body of strap members 51 and 52 thus maintaining a constant overall thickness. The thickness of the strap is determined by the requirements of the forces imposed thereon.

The extended nose straps of the present invention have proven to be quite effective in use. For given cuts with a given tool where the only difference is the substitution of the conventional strap for the extended nose strap, the use of the extended nose strap reduced not only the handle load required to make the cut substantially but also reduced the forces imposed on the several portions of the tool. In other instances it has been found that in the case of particular jaw pairs that would not operate satisfactorily in particular difficult situations the substitution of the extended nose straps for conventional straps for the most part eliminated the difficulties. Indeed measurements have shown that the out of plane forces separating the cutting edges are approximately 25 times greater when using the conventional straps in a particular tool than when using the extended nose straps of the present invention on that same tool.

lclaim:

1. In a heavy-duty compression tool of the type wherein the jaw portion comprises two generally flat sided jaw members each pivotally joined at an intermediate point to a pair of cross strap members positioned one on each side of said jaw members;

means for preventing out of plane distortion between the forward portion of said jaw members, comprising rigid forward extensions of both said cross strap members overlying in close association substantially all of the flat surface on both sides of both said jaw members in the forward portion of each said jaw member with at least the periphery of each said forward extension contacting the associated side of both said jaw members in wiping relationship.

2. A heavy-duty compression tool as claimed in claim 1 wherein a work receiving slot is provided in both said forward extensions, said slot having a width closely approximating, but slightly in excess of the maximum diameter of the work intended to be handled by the tool and a length such that the work remains between working portions of said jaws.

3. A heavy-duty compression tool as claimed in claim 2 wherein the wiping faces of said cross strap members and said jaw members are surface ground to minimize binding. 

1. In a heavy-duty compression tool of the type wherein the jaw portion comprises two generally flat sided jaw members each pivotally joined at an intermediate point to a pair of cross strap members positioned one on each side of said jaw members; means for preventing out of plane distortion between the forward portion of said jaw members, comprising rigid forward extensions of both said cross strap members overlying in close association substantially all of the flat surface on both sides of both said jaw members in the forward portion of each said jaw member with at least the periphery of each said forward extension contacting the associated side of both said jaw members in wiping relationship.
 2. A heavy-duty compression tool as claimed in claim 1 wherein a work receiving slot is provided in both said forward extensions, said slot having a width closely approximating, but slightly in excess of the maximum diameter of the work intended to be handled by the tool and a length such that the work remains between working portions of said jaws.
 3. A heavy-duty compression tool as claimed in claim 2 wherein the wiping faces of said cross strap members and said jaw members are surface ground to minimize binding. 